Anterior horn cells are affected in :
**Core Concept**
Anterior horn cells, also known as alpha motor neurons, are a type of motor neuron located in the spinal cord's anterior horn. These cells play a crucial role in transmitting signals from the central nervous system to skeletal muscles, facilitating voluntary movements.
**Why the Correct Answer is Right**
The correct answer involves the pathology of amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disease characterized by the degeneration of motor neurons. In ALS, both the upper motor neurons (corticospinal tract) and lower motor neurons (anterior horn cells) are affected, leading to muscle weakness, atrophy, and paralysis. The involvement of anterior horn cells in ALS is due to the loss of motor neurons, which disrupts the normal transmission of signals from the spinal cord to skeletal muscles.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anterior horn cells are not primarily affected in multiple sclerosis, which is an autoimmune disease that affects the central nervous system, particularly the white matter. While multiple sclerosis can cause motor symptoms, it primarily affects the optic nerve, brainstem, and spinal cord.
**Option B:** This option is incorrect because anterior horn cells are not primarily affected in Parkinson's disease, which is a neurodegenerative disorder characterized by the loss of dopamine-producing neurons in the substantia nigra. Parkinson's disease primarily affects movement, causing symptoms such as tremors, rigidity, and bradykinesia.
**Option C:** This option is incorrect because anterior horn cells are not primarily affected in peripheral neuropathy, which is a condition characterized by damage to the peripheral nerves. While peripheral neuropathy can cause muscle weakness and atrophy, it primarily affects the peripheral nerves, rather than the spinal cord's anterior horn cells.
**Clinical Pearl / High-Yield Fact**
One key aspect of ALS is the selective vulnerability of motor neurons, which is thought to be related to the presence of abnormal proteins, such as TDP-43 and SOD1, within the motor neurons.
**Correct Answer:** A.